1. Field of the Invention
The present invention relates to a method for producing a liquid discharging head adapted for use in a printer constituting an output terminal for a copying apparatus, a facsimile apparatus, a word processor or a host computer or in a video printer, and more particularly to a method for producing a liquid discharging head having a substrate on which formed is an electrothermal converting element for generating thermal energy to be used for recording. More specifically, it relates to a method for producing a liquid discharging head adapted for use in a liquid discharge recording apparatus which executes recording by discharging recording liquid (such as ink) as a flying droplet from a discharge opening (orifice) and depositing the liquid onto a recording medium.
2. Related Background Art
There is already known so-called bubble jet recording method, namely an ink jet recording method of providing ink with an energy such as heat to cause a state change involving an abrupt volumic change in the ink, discharging ink from the discharge opening by an action force based on such state change and depositing the ink onto a recording medium to form an image. The recording apparatus employing such bubble jet recording method is generally provided, as disclosed in the U.S. Pat. No. 4,723,129, with a discharge opening for discharging ink, an ink path communicating with the discharge opening and an electrothermal converting member provided in the ink path and serving as energy generating means for generating energy for discharging the ink.
Such recording method has various advantages for example of recording an image of high quality at a high speed with a low noise level, and recording an image of a high resolution or even a color image with a compact apparatus since, in the head executing such recording method, the ink discharge openings can be arranged with a high density. For this reason, the bubble jet recording method is recently employed in various office equipment such as printers, copying machines, facsimile apparatus etc., and even in industrial systems such as fabric dyeing apparatus.
With the spreading of the bubble jet technology into various fields, there are appearing various demands explained in the following.
For example, in order to satisfy a demand for improving the energy efficiency, there is conceived optimization of the heat generating member, such as adjustment of the thickness of the protective film for the heat generating member. This method is effective in improving the efficiency of propagation of the generated heat to the liquid.
Also for obtaining the image of high quality, there is proposed a driving method for liquid discharge capable of realizing a faster ink discharging speed and satisfactory ink discharge based on stable bubble generation, and, for achieving high-speed recording, there is proposed an improved shape of the liquid path for realizing the liquid discharge head with a faster refilling speed of the liquid into the liquid path.
Also in relation to the basic principle of liquid discharge, investigations have been made to provide a novel liquid discharging method utilizing the bubble that has not been available and a head adapted for use in such method, and such method and head are disclosed for example in the Japanese Patent Application Laid-open No. 9-201966.
In the following there will be explained, with reference to FIGS. 21A to 21D and 22, the conventional liquid discharging method and the head therefor disclosed in the Japanese Patent Application Laid-open No. 9-201966. FIGS. 21A to 21D are cross-sectional views along the liquid path, for explaining the discharging principle of the conventional liquid discharge head, and FIG. 22 is a partially broken perspective view of the liquid discharge head shown in FIGS. 21A to 21D. The liquid discharge head shown in FIGS. 21A to 21D and 22 has a basic configuration of controlling the pressure propagating direction based on the bubble and the growing direction thereof, thereby improving the discharging force and the discharging efficiency.
In the following description, the expression xe2x80x9cupstreamxe2x80x9d or xe2x80x9cdownstreamxe2x80x9d refers to the liquid flowing direction from the liquid supply source, then through above a bubble generating area, toward the discharge opening.
The xe2x80x9cdownstream sidexe2x80x9d relating to the bubble itself refers to the side of discharge opening of the bubble, considered principally acting on the discharge of the liquid droplet. More specifically, it means the downstream side in the flowing direction mentioned above or the direction in the above-described configuration with respect to the center of the bubble, or means a bubble generated in an area of the heat generating member in the downstream side with respect to the areal center thereof.
Also the xe2x80x9ccomb-tooth shapexe2x80x9d means a shape in which movable members are as a common member at the fulcrum ends thereof and are liberated in front of the free ends thereof.
In the configuration shown in FIGS. 21A to 21D, the liquid discharge head is provided, on an element substrate 1101, with a heat generating member 1102 as a discharge energy generating element for giving thermal energy to the liquid for the discharge thereof, and a liquid path 1103 is provided on the element substrate 1101, corresponding to the heat generating member 1102. The liquid path 1103 communicates with a discharge opening 1104 and also with a common liquid chamber 1105 for supplying plural liquid paths 1103 with the liquid, and receives, from the common liquid chamber 1105, with the liquid of an amount matching the discharged amount thereof.
On the element substrate 1101 in the liquid path 1103, a plate-shaped movable member 1106, composed of an elastic material such as metal and having a flat portion, is formed in the form of a beam supported at an end, so as to face the aforementioned heat generating member 1102. An end of the movable member 1106 is fixed to a support member 1107 formed by patterning photosensitive resin or the like on the wall of the liquid path 1103 or on the element substrate 1101, whereby the movable member 1106 is supported by the support member 1107 with a fulcrum 1108.
The movable members 1106 are constructed in a comb-tooth shape, whereby the movable member 1106 can be prepared easily and inexpensively, and can be easily aligned with the support member 1107.
The movable member 1106 is so positioned as to be opposed to and to cover the heat generating member 1102, with a distance of about 15 xcexcm therefrom, and to have the fulcrum 1108 at the upstream side in the main flowing direction of the liquid, caused by the liquid discharging operation, from the common liquid chamber 1105 through above the movable member 1106 toward the discharge opening 1104 and to have the free end 1109 at the downstream side with respect to the fulcrum 1108. A space between the heat generating member 1102 and the movable member 1106 constitutes a bubble generating area 1110.
Heat generation by the heat generating member 1102 applies heat to the liquid in the bubble generating area 1110 between the movable member 1106 and the heat generating member 1102, thereby generating a bubble in the liquid based on a film boiling phenomenon as described in the U.S. Pat. No. 4,723,129 (see. FIG. 21B). The bubble 111 and the pressure resulting from the generation thereof are preferentially applied to the movable member 1106, which in response displaces to open widely toward the discharge opening 1104 about the fulcrum 1108, as shown in FIGS. 21B and 21C or in FIG. 22. Based on the displacement of the movable member 1106 or the displaced state thereof, and also on a fact that the front end portion of the bubble has a certain width, the pressure resulting from the generation of the bubble 1111 can more easily propagate toward the discharge opening 1104, whereby a basic improvement can be attained in the discharging efficient of the liquid droplet 1133, discharging force thereof or discharging speed thereof. A reference number 1130 indicates the areal center of the heat generating member.
As explained in the foregoing, the technology disclosed in the Japanese Patent Application Laid-open No. 8-4892 is to positively control the bubble by positioning the fulcrum and the free end of the movable member in the liquid path in such a manner that the free end is provided at the side of the discharge opening or at the downstream side, and by positioning the movable member so as to be opposed to the heat generating member or the bubble generating area.
Also a liquid discharge head shown in FIG. 23 has an element substrate 1201, a heat generating member 1202, a liquid path 1203, a discharge opening 1204, a common liquid chamber 1205 and a bubble generating area 1209 which are similarly constructed as those shown in FIGS. 21A to 21D and which will not, therefore, be explained further.
In the liquid discharge head shown in FIG. 23, the movable member 1206 formed as a beam supported at an end is provided, at an end thereof, with a step difference portion 1206a, and is directly fixed to the element substrate 1201. Thus the movable member 1206 is supported on the element substrate 1201 with a fulcrum 1207 and has a free end 1208 at the downstream side of the fulcrum 1207.
A gap of about 1 to 20 xcexcm is formed between the movable member and the heat generating member by forming a support member in the fixing portion of the movable member or forming a step difference in the fixing portion of the movable member as explained in the foregoing, thereby achieving a sufficient improvement in the liquid discharging efficiency by the movable member. Thus, in the liquid discharge head based on the above-described novel principle of liquid discharge, there can be attained a multiplying effect of the generated bubble and the movable member displaced thereby, thus achieving efficient discharge of the liquid present in the vicinity of the discharge opening, thereby improving the liquid discharging efficiency in comparison with the discharging method or head of the conventional bubble jet system.
The present invention is to improve the fundamental discharge characteristics of the basically conventionally method of discharging liquid by forming a bubble, particularly a bubble based on film boiling, in the liquid path, to a level that cannot be anticipated before.
The present inventors have made intensive investigations in order to provide a novel liquid droplet discharging method utilizing the conventionally unavailable bubble and a head utilizing such method. In these investigations, there have been executed first technical analysis on the function of the movable member in the liquid path, analyzing the principle of the mechanism of the movable member in the liquid path, a second technical analysis on the principle of liquid droplet discharge by the bubble, and third technical analysis on the bubble forming area of the heat generating member for bubble formation, and, through these analyses, there has been established a completely novel technology of positively controlling the bubble by positioning the fulcrum and the free end of the movable member in such a manner that the free end is provided at the side of the discharge opening or at the downstream side and by positioning the movable member so as to be opposed to the heat generating member or the bubble generating area.
Then, in consideration of the effect of the energy of the bubble itself on the discharge amount, there is obtained knowledge that the growing component in the downstream side of the bubble is the largest factor capable of drastically improving the discharge characteristics. More specifically, it has been found that the efficient conversion of the growing component in the downstream side of the bubble toward the discharging direction leads to an improvement in the discharge efficiency and discharge speed.
It has further been found that structural consideration is desirable on the movable or the liquid path relating to the heat generating area serving to form the bubble, for example relating to the bubble growth in the downstream side with respect to the central line passing through the areal center of the electrothermal converting member in the liquid flowing direction, or in the downstream side of the bubble with respect to the areal center of the area contributing to the bubble generation.
It has further been found that the refilling speed can be significantly improved by giving consideration to the arrangement of the movable member and the structure of the liquid supply path.
Also there has been found a difficulty in cutting the element substrate bearing the movable members from a wafer with a dicing saw, that the production yield is lowered by breaking of the movable member by the pressure of water at the cutting operation or by the air pressure generated by the high-speed rotation of the diamond blade, since a gap of about 1 to 20 xcexcm is present between the movable member and the heat generating member.
An object of the present invention is to provide a liquid discharge head capable, at least at the cutting of the element substrate bearing the movable member, of preventing breakage or deformation of the movable member by the pressure of grinding water or by the air pressure generating by the high-speed rotation of the dicing blade, thereby enable stable manufacture with a high production yield. Another object of the present invention is to provide a liquid discharge head and a liquid discharge apparatus of high reliability with stable discharging characteristics, in liquid discharge utilizing the displacement of the free end of the movable member. Still another object of the present invention is to provide a method for producing the liquid discharge head, capable of forming the movable member etc. thereof with a high precision and a high density.
Still another object of the present invention is to provide a method for producing the liquid discharge head, capable of improving the yield safely without complicating the process, in case the method includes a step of cutting the element substrate bearing the movable member from a wafer by dicing operation.
The above-mentioned objects can be attained, according to the producing method of the present invention, by a liquid discharge head comprising a discharge opening for discharging liquid, a liquid path communicating with the discharge opening for supplying the discharge opening with the liquid, a substrate provided with a heat generating member for generating a bubble in the liquid filled in the liquid path, and a movable member supported by the substrate in a position opposed to the heat generating member on the substrate, with a gap to the substrate and with the free end at the side of the discharge opening, wherein the free end of the movable member is displaced, by the pressure generated by the generation of the bubble, toward the discharge opening about a fulcrum portion present in the vicinity of the supporting portion for the movable member on the substrate, thereby discharging the liquid from the discharge opening.
Further, in order to attain the above-mentioned object, a method for producing a liquid discharge head provided with an element substrate and a ceiling plate which are fixed in a mutually opposed state, plural liquid path walls provided between the ceiling plate and the element substrate and defining plural liquid paths, plural discharge energy generating elements provided in parallel manner on the surface of the element substrate so as to be respectively positioned in the plural liquid paths, and plural movable members provided on the element substrate so as to respectively oppose to the plural discharge energy generating elements and formed like a cantilever, fixed at the upstream ends in the flowing direction of the liquid in the liquid paths and having free ends at the downstream ends, comprises following steps of:
forming a gap forming member in a position, on the surface provided with the discharge energy generating element of the element substrate, corresponding to a bubble generating area where a bubble is generated in the liquid by the thermal energy generated by the discharge energy generating element;
forming a first material layer to constitute the movable member on the gap forming member;
patterning an anti-etching protective film in the form of the movable member;
forming a second material layer to constitute the liquid path walls so as to cover the upper and lateral faces of the patterned anti-etching protective film;
removing a portion corresponding to the liquid path in the second material layer by etching, thereby forming the liquid path walls and the liquid path;
cutting the element substrate to be plurally separated between the step of patterning the movable member and the step of forming the second material layer; and
removing the gap forming member after the formation of the liquid path.
In order to attain the object mentioned above, a method for producing a liquid discharge head provided with an element substrate and a ceiling plate which are fixed in a mutually opposed state, plural liquid path walls provided between the ceiling plate and the element substrate and defining plural liquid paths, plural discharge energy generating elements provided in parallel manner on the surface of the element substrate so as to be respectively positioned in the plural liquid paths, and plural movable members provided on the element substrate so as to respectively oppose to the plural discharge energy generating elements and formed like a cantilever, fixed at the upstream ends in the flowing direction of the liquid in the liquid paths and having free ends at the downstream ends, comprises steps of:
forming a gap forming member in a position, on the surface provided with the discharge energy generating element of the element substrate, corresponding to a bubble generating area where a bubble is generated in the liquid by the thermal energy generated by the discharge energy generating element;
forming a first material layer to constitute the movable member on the gap forming member;
forming an anti-etching protective film in the form of the movable member on the first material layer;
patterning the first material layer thereby forming the movable member;
forming a second material layer to constitute the liquid path walls so as to cover the upper and lateral faces of the patterned anti-etching protective film;
removing a portion corresponding to the liquid path in the second material layer by etching, thereby forming the liquid path walls and the liquid path;
removing the gap forming member after the formation of the liquid path; and
cutting the element substrate to be plurally separated between the step of forming the movable member and the step of removing the gap forming member.
In order to attain the object, a method for producing a liquid discharge head at least includes:
a discharge opening for discharging liquid;
a liquid path communicating with the discharge opening for supply of the liquid thereto;
a substrate provided with a heat generating member for generating a bubble in the liquid filled in the liquid path; and
a movable member supported by and fixed to the substrate in a position opposed to the heat generating member on the substrate with a gap from the substrate and with a free end at the side of the discharge opening;
wherein the free end of the movable member is displaced toward the discharge opening about a fulcrum portion formed in the vicinity of the fixing portion of the movable member on the substrate by the pressure induced by the generation of the bubble, whereby the liquid is discharged from the discharge opening, the method comprising steps of:
forming a gap forming member on the substrate for forming the gap;
forming the movable member on the gap forming member;
cutting the substrate to be plurally separated; and
removing the gap forming member.
Further, to attain the above object, a method for producing a liquid discharge head includes:
a discharge opening for discharging liquid;
a liquid path communicating with the discharge opening for supply of the liquid thereto;
a substrate provided with a heat generating member for generating a bubble in the liquid filled in the liquid path; and
a movable member supported by and fixed to the substrate in a position opposed to the heat generating member on the substrate with a gap from the substrate and with a free end at the side of the discharge opening;
wherein the free end of the movable member is displaced toward the discharge opening about a fulcrum portion formed in the vicinity of the fixing portion of the movable member on the substrate by the pressure induced by the generation of the bubble, whereby the liquid is discharged from the discharge opening, the method comprising steps of:
forming a protective layer on the substrate in order to form a plurality of the substrates on a single wafer;
forming a gap forming member on the substrate and on the protective layer for forming the gap;
forming a base material for the movable member on the substrate, the protective layer and the gap forming member;
patterning the base material for the movable member thereby forming the movable member;
removing the protective layer;
filling a gap filling material in the gap;
cutting and separating each substrate from the wafer; and
removing the gap forming member by washing.
Furthermore, to attain the above object, a method for producing a liquid discharge head includes:
a discharge opening for discharging liquid;
a liquid path communicating with the discharge opening for supply of the liquid thereto;
a substrate provided with a heat generating member for generating a bubble in the liquid filled in the liquid path; and
a movable member supported by and fixed to the substrate in a position opposed to the heat generating member on the substrate with a gap from the substrate and with a free end at the side of the discharge opening;
wherein the free end of the movable member is displaced toward the discharge opening about a fulcrum portion formed in the vicinity of the fixing portion of the movable member on the substrate by the pressure induced by the generation of the bubble, whereby the liquid is discharged from the discharge opening, the method comprising steps of:
forming a protective layer on the substrate in order to form a plurality of the substrates on a single wafer;
separating each substrate by cutting from the wafer in a state in which a gap filler is filled in the gap between the movable member and the substrate; and
removing the gap filler by washing after the step of separation by cutting.
The method for producing such liquid discharge head forms the movable member and the walls of the liquid path directly on the element substrate, utilizing the general manufacturing steps for the semiconductor device such as photolithography and etching, whereby these components can be formed with a high precision and with a high density. Also, in comparison with the case of separately preparing and thereafter assembling these components, there can be dispensed with the assembling step so that the manufacturing process can be simplified. Furthermore, as the movable member need not be adhered with an adhesive material, there can be avoided the contamination of the liquid inside the liquid path or the bubble generating area by such adhesive material.
Also in the step of forming the walls of the liquid path, an orifice plate having plural discharge openings respectively communicating with plural liquid paths may be formed in a position at the front end face of the walls of such plural liquid paths, simultaneously with the formation of the walls of the plural liquid paths on the element substrate. This method directly forms the orifice plate on the element substrate, thereby dispensing with the step of adhering the orifice plate and further simplifying the producing method for the liquid discharge head.
It is preferable, in a step of patterning an anti-etching protective film, to pattern a first material layer constituting the movable member, simultaneously an anti-etching protective film.
It is preferable to form the movable member, the walls of the plural liquid paths and the orifice plate with silicon nitride, a gap forming member with phosphor silicate glass (PSG) and an anti-etching protective film with aluminum.
A same material is preferably contained in the element substrate, movable member, walls of the liquid path, orifice plate and ceiling plate. In this manner, in case the temperature of the liquid discharge head is elevated by the thermal energy generated by the energy generating elements, it is rendered possible to suppress the stress resulting from the difference in the linear expansion coefficients of the members constituting the liquid discharge head. Consequently the mechanical characteristics of the liquid discharge head are improved, thereby improving the liquid discharge characteristics. More specifically it is preferred to constructing the element substrate by forming plural energy generating elements on a silicon substrate and forming the movable member, walls of the liquid path, orifice plate and ceiling plate with silicon nitride.
It is furthermore preferred to include a step of forming plural heater drivers for respectively driving the energy generating elements, respectively corresponding to the plural energy generating elements and in a linear array parallel to the arranged direction of the energy generating elements. In this manner the wirings can be arranged in an efficient layout on the surface of the element substrate, and the element substrate can be made compacter in chip size. More specifically, the heater driver can be composed of a transistor of offset MOS type, LDMOS type or LVMOS type with a voltage endurance of 10 to 50 V, in order to reduce the pitch of the heater drivers. Also the energy generating element can be composed of TaSiN having a sheet resistance of 50 xcexa9/xe2x96xa1 or higher, thereby enabling to drive the energy generating elements with a pitch of several micrometers.
In the above-described producing method, in separating each heater substrate by dicing operation after plural heater substrates bearing the movable members are formed on a single wafer, there is included a coating step for a gap filling material for filling the gap between the heater substrate and the movable member prior to the cutting operation, in order to protect the movable member from the pressure of the grinding water or the air pressure generated by the high-speed rotation of the diamond blade, thereby resolving the drawback of loss of the production yield resulting from the breakage of the movable member.